The present invention relates to coaxial resonators having a reduced number of components and which can be manufactured by a simplified process, and to dielectric filters and dielectric duplexers including such resonators.
As shown in FIG. 8 which is an equivalent circuit diagram of the present invention, dielectric duplexers 40 for use in communications devices for transmitting and receiving high-frequency signals of hundreds of megahertz to several gigahertz comprise a band-reject dielectric filter 42 on the receiving side, and a band-pass dielectric filter 43 on the receiving side which are electrically connected to a common antenna ANT.
The band-reject dielectric filter 42 and the band-pass dielectric filter 43 each include a plurality of coaxial dielectric resonators 11, 11, 11 mounted on an electrically conductive pattern 71 on a substrate 70 and electrically connected together by an inductance L, capacitors C, etc. (see FIG. 9 of the invention). Some of the inductance L and capacitors C in FIG. 9 are formed directly on the pattern 71 on the substrate 70.
The coaxial dielectric resonators to be mounted on the substrate 70 include a xc2xc wavelength resonator 11. With reference to FIG. 11, this device comprises a dielectric block 12 having a through- bore 13 extending through opposite end faces thereof, and a conductor layer 14 formed over the outer peripheral surface of the block 12 except one end face thereof and over the block inner surface defining the through-bore 13. This resonator causes electromagnetic waves having a wavelength equal to xc2xc of the length of the resonator to resonate within the dielectric block 12.
The resonators 11 mounted on the substrate 70 include one electrically connected in series with an electric element such as an inductance or a capacitor, as indicated at 10 in the equivalent circuit diagram of FIG. 8. The resonator 11 is connected to the electric element 22 conventionally by using a tubular member 90 which is made by shaping a conductive metal into a tubular form as shown in FIG. 10 and which has a tongue 91 projecting from one end of the tubular member The resonator 11 is electrically connected in series with the electric element 22 by inserting the tubular member 90 into the through-bore 13 of the resonator 11, as shown in FIG. 10, mounting the resonator 11 on the substrate 70, and thereafter soldering the tongue 91 of the tubular member 90 to a lead 23 of the electric element 22 as at 93 on a conductive plate 92, as shown in FIG. 11. electric element 22 as at 93 on a conductive plate 92 as shown in FIG. 11.
The electrical connection of the resonator 11 to the inductance or like electric element 22 thus necessitates the tubular member 90 and the conductive plate 92, which therefore increase the number of work steps involved in mounting and the number of parts, while the substrate 70 requires a space for providing the conductive plate 92. Accordingly, difficulties are encountered in making dielectric filters 41 or dielectric duplexers 40 comprising resonators 11 more compact.
An object of the present invention is to provide a coaxial resonator which can be electrically connected to an inductance or like electric element easily to reduce the number of work steps for mounting and the number of parts, and a dielectric filter and a dielectric duplexer which comprise the resonator and which can be compacted and installed in a diminished space.
To fulfill the above object, the present invention provides a coaxial resonator comprising a dielectric block having a through-bore extending through opposite end faces thereof, and a conductor layer formed over an outer peripheral surface of the block except one end face thereof and over a block inner surface defining the through bore for causing electromagnetic waves to resonate within the dielectric block. A lead-equipped electric element has its lead inserted in the through-bore and electrically connected to the conductor layer over the bore-defining inner surface with a braze filler metal or electrically conductive adhesive, and the lead is fixed in the through-bore.
The present invention provides a dielectric filter including a plurality of coaxial resonators. The coaxial resonator described is used as at least one of these coaxial resonators.
The present invention further provides a dielectric duplexer comprising a band-reject filter for transmitting and a band-pass filter for receiving which are electrically connected to an antenna ANT. The dielectric filter described is used as the band-reject filter and/or the band-pass filter.
The coaxial resonator of the present invention can be electrically connected to the lead of an inductance or like electric element by inserting the lead directly into the through-bore of the resonator and brazing the lead to the bored portion with a braze filler metal. An electrically conductive adhesive can be used in place of the braze filler metal.
The coaxial resonator of the present invention requires none of parts such as a tubular member and conductive plate, thus serving to reduce the number of parts. Because the lead of the electric element is joined to the resonator by direct brazing or using a conductive adhesive, the number of work steps conventionally needed for mounting can be diminished. The reductions in the number of parts and the number of work steps achieve improvements in the reliability of the product.
The dielectric filter and the dielectric duplexer of the present invention include a coaxial resonator, which can be electrically connected directly to the lead-equipped electric element without necessitating a conductive plate or the like. This serves to reduce the number of work steps and the number of parts, further eliminating the need for a space for the provision of the conductive plate. The filter and the duplexer can therefore be made more compact. Because the coaxial resonator of the present invention has an improved reliability as stated above, the filter and the duplexer including the resonator are also improved in reliability.